Conventionally, image display devices having pixels each of which is composed of three sub-pixels for displaying three primary colors of red (R), green (G), and blue (B) so as to perform color display have been spread widely. Besides, it has been known widely that in an image display device, the following filtering processing of various types are carried out: contour enhancement processing performed by superposing high-frequency components extracted with use of a high-pass filter; and smoothing processing performed by removing high-frequency components with use of a low-pass filter. For example, by performing the contour enhancement processing, a sharp image with higher definition can be obtained. Alternatively, by performing the smoothing processing, noises are removed, whereby a smoother image can be obtained.
Still further, in order to achieve further higher definition, a technique for generating a display image by performing the following steps has been proposed: generating an image with sub-pixel-level fineness by interpolation, generating an enhanced image in which components belonging to a specific frequency band of the sub-pixel-level image are enhanced, and performing sub-pixel rendering processing (see, for example, JP2005-141209A).